HEAT OVEN to 400F/204C and place rack in top ⅓ of oven. Spray a 7-8 inch (18-20cm) square pan with oil.

MAKE POTATO/ROOT VEGETABLE TOPPING: °Boil: Place potatoes and other root vegetables in a medium pot. Add enough cold water to cover veggies by 1 inch (2.5 cm). Add 2-3 tsp salt. Bring to boil. Lower heat to medium and gently boil for about 15 minutes or until soft and fork tender. °Drain: Drain vegetables in a colander and return to the pot. On medium heat, shake cooked vegetables to evaporate water for 1 minute. °Mash: Add butter, green onions and 3 tablespoon Parmesan (if using) and 1-2 tablespoons milk/cream if you like (not too much milk - you don't want the potatoes soupy). Mash with a fork or potato masher. Do not use a food processor or immersion blender. Taste and add salt and pepper if needed. Set aside.

MAKE FILLING LAYER: ° Sauté veggies: Heat oil in large skillet to medium-high heat. Add onions and carrots. Sauté for 5 minutes, stirring occasionally. ° Sauté 'beef': Add plant based beef and chop it up into small pieces with a rubber spatula or wooden spoon. Stir in garlic, rosemary, thyme, salt, pepper, tomato paste, Worcestershire sauce. Sauté, stirring occasionally, for 4 minutes, until 'beef' is brown. ° Make gravy: Stir in flour for 2 minutes. Add broth/wine, frozen corn and spinach. Stir to combine well. Let simmer for 3-4 minutes to let the mixture thicken for a rich gravy. Taste and adjust seasonings.

ASSEMBLE AND BAKE/BROIL: Spoon 'beef' filling layer into casserole dish. Top with a thick layer of ~3 cups/630 grams root vegetable mash (you may not need all the mash you made). Fluff topping with fork. Sprinkle on 1 tablespoon grated Parmesan if desired. °Bake for 15 minutes. Note 4. Turn oven to Broil. °Broil for 2-3 minutes until topping is golden brown. Top with extra green onions if you like. °Rest on counter for 10 minutes. Serve.